Technical Information

Dimensional Specifications

DIN 931 & DIN 933

The drawing below shows unthreaded fasteners. The thread length of Metric bolts manufactured to DIN 931 and 933, with diameter d and thread length t, is:

t = 2d + 6mm up to 125mm;
t = 2d + 12mm from 125mm until 200mm;
2d + 25mm at 200mm and over
.

(Click on the image to enlarge)

din 931

BS 1083

The drawing below shows unthreaded fasteners. The thread length of BSW or BSF bolts manufactured to BS1083, with diameter d and thread length t, is t = 2d.

(Click on the image to enlarge)

bs1083

BS 1768

The drawing below shows unthreaded fasteners. The thread length of UNC or UNF bolts manufactured to BS1768, with diameter d and thread length t, is:

t = 2d + 1/4" up to a length of 6", where the formula becomes t = 2d + 1/2".

(Click on the image to enlarge)

bs1768

How to measure

Measuring bolt diameter

Bolts can be accurately measured using a vernier.

For metric bolts, the prefix 'M' is added to denote Metric. For example, a 4mm diameter bolt is commonly known as an 'M4' bolt. Imperial bolts are measured in inches.

Measuring bolt length

The length of a Hexagon bolt is determined by measuring from underneath the head to the end of the bolt. If the bolt has a countersunk head, the full length of the bolt including head is measured.

Measuring threads

Metric bolts are identified by measuring the distance between the threads - a 1mm pitch bolt has 1mm between the threads.

The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

See the thread charts on this page for more information.

A thread gauge can be used to identify bolts and nuts, although they are not in common usage. The Thread Detective is a quick and easy solution to the problem of identifying bolt and nut threadforms, allowing quick and precise identification of Metric, UNC & UNF bolts and nuts.

ranger

Thread Detective - Thread Identifier

Thread Charts

Metric

Metric bolts are identified by measuring the distance between the threads in millimetres - a 1mm pitch bolt has 1mm between the threads.

Diameter Coarse Fine Extra Fine Super Fine
M1 0.25 0.2
M1.6 0.35 0.2
M2 0.4 0.25
M2.5 0.45 0.35
M3 0.5 0.35
M4 0.7 0.5
M5 0.8 0.5
M6 1.0 0.75
M7 1.0 0.75
M8 1.25 1.0 0.75
M10 1.5 1.25 1.0 0.75
M12 1.75 1.5 1.25 1.0
M14 2.0 1.5 1.25 1.0
M16 2.0 1.5 1.0
M18 2.5 2.0 1.5 1.0
M20 2.5 2.0 1.5 1.0
M22 2.5 2.0 1.5 1.0
M24 3.0 2.0 1.5 1.0

Imperial

The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

Diameter UNC UNF BSW BSF
No.4 40 48
No.6 32 40
No.10 / 3/16 24 32 24 32
1/4 20 28 20 26
5/16 18 24 18 22
3/8 16 22 16 20
7/16 14 20 14 18
1/2 13 20 12 16
9/16 12 18 12 16
5/8 11 18 11 14
3/4 10 16 10 12

BA

BA is an imperial threadform. The thread pitch of an imperial bolt is denoted by the amount of threads per inch.

BA number TPI Dia (inch)
6 47.9 0.11
4 38.5 0.142
3 34.8 0.161
2 31.4 0.185
0 25.4 0.236

Mechanical Properties

Metric

Property 4.6 8.8
<= M16
8.8
> M16
10.9 12.9
Min Tensile N/mm2 400 800 830 1040 1220
Min Lower Yield Stress N/mm2 240
Min Proof Stress N/mm2 640 660 940 1100
Hardness Min HRC 22 23 32 39
Hardness Max HRC 32 34 39 44

BSW & BSF

Property R T V
Min Tensile tonf/in2 45 55 65
Min Yield Stress tonf/in2 34 41 52
Hardness Brinell 201/285 248/335 293/370

UNC & UNF

Property S T V
Min Tensile tonf/in2 50 55 65
Proof Stress tonf/in2 38 41 49.5
Hardness Brinell 223/310 248/335 293/370

Torque figures

Metric coarse

M6 M8 M10 M12 M14 M16 M20 M22 M24 M30 M36 M42
4.6 kgf m 0.46 1.12 2.23 3.89 6.21 9.65 18.8 25.6 32.6 64.7 113 181
8.8 kgf m 1.23 3.0 5.95 10.35 16.5 25.7 50.2 68.3 86.6 172 300 478
10.9 kgf m 1.73 4.22 8.35 14.6 23.2 36.2 70.7 96 122 242 423 678

Metric fine

M6 M8 M10 M12 M14 M16 M20 M22 M24 M30 M36
4.6 kgf m 0.50 1.20 2.35 4.24 6.72 10.3 20.9 28.1 35.4 71.5 120
8.8 kgf m 1.34 3.2 6.25 11.3 17.9 27.3 55.7 75.0 94.5 189 316
10.9 kgf m 1.90 4.52 8.8 15.9 25.2 38.5 78.5 105 132 268 448

UNC

1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1 1.1/8 1.1/4 1.3/8 1.1/2
S lbf ft 9 20 35 56 85 123 170 300 485 730 1035 1460 1920 2540
T lbf ft 10 21 36 58 88 127 175 311 500 750 1065 1500 1965 2610
V lbf ft 12 25 45 73 111 160 212 393 632 950 1345 1900 2480 3300

UNF

1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1 1.1/8 1.1/4 1.3/8 1.1/2
S lbf ft 11 22 40 62 96 137 192 335 535 795 1075 1500 2040 2690
T lbf ft 12 23 41 64 99 141 195 345 650 820 1100 1540 2100 2760
V lbf ft 14 28 50 81 125 180 238 435 695 1000 1390 1950 2650 3500

BSW

1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1 1.1/8 1.1/4 1.3/8 1.1/2
R lbf ft 8 17 30 47 70 105 145 255 410 620 875 1235 - 2150
V lbf ft 12 25 45 72 107 160 210 390 628 945 1330 1890 - 3280

BSF

1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1 1.1/8 1.1/4 1.3/8 1.1/2
R lbf ft 9 18 32 51 77 112 155 268 432 650 930 1300 1730 2270
V lbf ft 14 27 49 78 118 173 224 410 660 995 1420 1990 2630 3480



All technical information is provided as a guideline only - use at your own risk. Thomas Smith Fasteners will not accept liability for any expense, damage or loss you may incur as a result of using this information.

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